1. Field of the Invention
This invention relates to recording and reproducing techniques for use with information signals having a wide bandwidth and, more particularly, to such techniques whereby a wide bandwidth color video signal may be recorded on a video disc by timebase expanding the luminance component and timebase compressing the color difference components prior to recording.
2. Description of the Prior Art
Composite color video signals used in high definition television transmission (HDTV) exhibit a wider bandwidth than conventional non-HDTV signals. For example, the bandwidth of the HDTV luminance component is on the order of about 20 MHz and the bandwidth of the HDTV red and blue color difference signals each is on the order of about 6 MHz. See, for example, Japanese Laid-Open Patent Document No. 58-38091.
It is expected that HDTV displays will be produced not only from broadcast HDTV signals, such as over-the-air or cable distribution transmission, but also from prerecorded television programs, such as prerecorded HDTV video discs. Because of the wide bandwidth of HDTV composite signals, satisfactory reproduction and display of an HDTV picture may require that the rotational speed of the video disc be relatively high, the track pitch in which successive tracks are recorded be reduced, and the wavelength of the light beam, such as the laser beam used to record the video signals, also should be reduced. At the present time, it is believed that some or all of these requirements still are under development. Hence, it is anticipated that substantial efforts and expense still may be needed to develop a commercially acceptable system in which the video disc is rotated at the proper speed, the track pitch is sufficiently fine and the wavelength of the recording laser beam is sufficiently low.
An alternative to recording a wide bandwidth HDTV signal contemplates a reduction in that bandwidth. Band compressing techniques are known, and it is thought that such techniques can be used to suitably reduce the bandwidth of the television signal for recording in accordance with conventional video recording techniques. However, depending upon the program content of the video signals, it has been observed that the use of band compression results in a television picture that is not natural looking. Furthermore, band compression circuitry used for wide band video signals are relatively complex.